Electrostatic discharge (ESD) protection circuitry is typically employed as an adjunct to other circuits, such as memories and processors, that include components that are sensitive to high voltage ESD events. In principle, ESD protection circuitry operates to provide some protection against high voltage by providing an alternative flow path for currents resulting from ESD events, so that the protected circuitry may continue to operate.
Some ESD protection circuits employ a diode as the primary protective component. However, this approach may present a relatively high impedance path for currents generated by ESD events, especially with respect to high voltage circuit inputs, such as memory programming pin inputs. When this happens, ESD currents may be directed into a node of the circuit that is to be protected, rather than into the preferred alternative path. Destruction of the circuit to be protected may result.